EFFECT OF SURFACE REFLECTANCE ON LIGHTING …

1 EFFECT OF SURFACE REFLECTANCE ON LIGHTING efficiency IN INTERIORS Rohini Singh1, Rajan Rawal2 1 Sikka Associate Architect, India 2 Faculty of Design, CEPT University, Ahmedabad, India ABSTRACT The paper attempts to analyze the relationship between SURFACE colour REFLECTANCE and LIGHTING power density for a given context. Analysis was based on digital modelling using validated LIGHTING simulation tool. The study establishes itself on the premise that grey value of colour can be presumed to calibrate the luminous character of light. Also, it evaluates the impact of vertical and horizontal planar interior elements REFLECTANCE and its impact on LPD. This is done through different scenarios derived from the basecase. All derived scenarios were then confirmed to the established visual comfort standard.

2 The results were collated to develop a colour chart. INTRODUCTION To comprehend the EFFECT of SURFACE REFLECTANCE on the LIGHTING effectiveness in interiors one needs to first grasp the meaning of interior space, its inter-relationship with energy efficiency , need for energy efficient strategies and the concepts of colour, light and REFLECTANCE . The above relation achieved hereby: Interior space, design: its meaning and nuances: Interior Space is concerned with anything that is found inside a space - walls, windows, doors, finishes, textures, light, furnishings and furniture. All of these elements are used by designers to develop a functional, safe, and aesthetically pleasing space. The goal is to produce a coordinated and harmonious space. Interior Space design is the process of shaping the experience of interior space, through the manipulation of spatial volume as well as SURFACE treatment.

3 Interior Space Design and Energy efficiency : a connotation to conscious designing: An interior space must adhere to code and regulatory requirements, and encourage the principles of environmental sustainability. Thereby, work of an interior space designing draws upon many disciplines including environmental psychology, LIGHTING , air-conditioning and aesthetics, etc. For more effective solutions and integrated approach, it is not only the domain of an interior designer or an architect but LIGHTING designers, HVAC consultant, civil engineer, the electrical engineers, etc. Interior LIGHTING Design and need for Energy Efficient strategies: an understanding: LIGHTING design as it applies to the interior built environment is both a science and an art. Comprehensive LIGHTING design requires consideration of the amount of functional light provided, the energy consumed, as well as the aesthetic impact supplied by the LIGHTING system.

4 LIGHTING includes use of both artificial light sources and natural daylight. But artificial LIGHTING represents a major component of energy consumption, accounting for a significant part of all energy consumed worldwide. Findings from a survey on energy end use intensities in commercial buildings, by Department of Energy, shows that LIGHTING consumes 25 30% of energy as shown in Figure 1. Also, commercial buildings, in particular Office Buildings are one of the largest components of Building Electricity Use. Figure 1 LIGHTING energy use compared to the other energy use Addressing Indian context, the share of electricity used, about 15 18 % of the total electricity generated is used for LIGHTING purposes. Thus it represents a critical component of energy use. Nevertheless there are several strategies available to minimize LIGHTING energy consumption in a building.

5 Many research standards like IESNA, IRC, etc. have developed scientific bases for LIGHTING , consider and identify SURFACE colour, REFLECTANCE , daylight availability, glare and, light distribution as prime issues to perpetuate efficient interiors. Interior Colour, Light, SURFACE REFLECTANCE and Efficient space design: Colour is one of the most dominant spatial elements in the interior built environment. Withal, colour of a space can subtly and even dramatically affect the LIGHTING of an Interior. It is so because colours of an interior SURFACE Proceedings of Building Simulation 2011: 12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November. - 2301 -can absorb or reflect light. In scientifically this very attribute of SURFACE colour is termed as SURFACE REFLECTANCE . It is due to this property of SURFACE colour; it can either enhance or nullify the distribution of light from the light source.

6 So in other words, they can have an EFFECT on the efficiency of the luminaire s distribution and consecutively the LIGHTING efficiency of the space. Studies have proved that as much as one-third of the energy use of a LIGHTING system depends upon the surrounding interior features, such as the ceiling height, windows, colour and reflectivity of room surfaces . Therefore, one would look at interior colour scheme as a unified whole, thinking in terms of space design, artificial LIGHTING and efficiency too. Furthermore, colour theories and models suggest that the amount of light reflecting from a colour SURFACE it is its value property or light REFLECTANCE value. This implies that grey value of colour alone can be presumed to calibrate the luminous character of light. It is not essential to address all colour ranges, hues, etc. Also, it is found that Munsell colour system simple, comprehendible and reliable for Grey value scale calibration.

7 ( Refer Figure 2) Figure 2 Munsell Colour system Energy efficiency is an attractive, but LIGHTING design must consider other factors such as visual comfort, health, etc. It is important to understand that only after the issues of quality proper luminance ratios, reduction of glare, etc. the quantity of light should be addressed. Many LIGHTING standards and codes have developed guidelines to select interior SURFACE colour wherein it suggesting a range of REFLECTANCE values of major surfaces of a room wall: floor: ceiling. However, the literature to date shows little consensus about preferred room SURFACE REFLECTANCE and workplane: partition REFLECTANCE in terms of both their energy performance and visual comfort conformity. Also not much consensus is apparent in terms of quantification with respect to LIGHTING loads consumed. In light of these deficiencies, it would be worth exploring the range of SURFACE REFLECTANCE for room surfaces , workplane and interior partitions, that are the most energy efficient and adhere to the visual balance of the space.

8 The underlying body of work aims to be effective and efficient, because it does not intend to decline the quality of the space and but consequently improve the performance of the LIGHTING of the space. Thereby purpose of this research is to study the EFFECT of SURFACE colour REFLECTANCE on LIGHTING efficiency of interior space whilst maintaining the visual comfort standards. (Figure 3) Interior SpaceLightColourEfficiency LIGHTING loadsenergy consumption harmony between them is essentialcolour and light interior space elementcolour and light define spaceapplication of light: aesthetics and functionconscious designingdominant spatial element Figure 3 Colour, light and energy efficiency - the domain of research focal point The objectives of the research are: To study quantitative aspect of colour, its REFLECTANCE and its EFFECT on distribution of light. To analyze the relationship between SURFACE colour REFLECTANCE of room surfaces , workplane and partitions.

9 To validate the performance of different REFLECTANCE combinations of the room surfaces by verifying against the optimal visual comfort requirements and determining the EFFECT on operating LIGHTING loads. Hence quantify its EFFECT on energy efficiency of the space To identify colours schemes that proves feasible within the premise of the study combinations of REFLECTANCE of the room surfaces . In order to accomplish this following methodology was adopted (Figure 4): Literature Survey of parameters involved. Proceedings of Building Simulation 2011: 12th Conference of International Building Performance Simulation Association, Sydney, 14-16 November. - 2302 -Quantify and analyze the hypothesis SURFACE colour effects performance distribution of light through Analytical Modelling; Simulation. Base Case Model derivation: Derive the Base case from of artificially lit Open Plan Offices typical of practice, define range of parameters for selection criteria and establish simulation model of these parameters.

10 Establishment of Case: Develop basic understanding of the relationship between REFLECTANCE , Luminance, Illuminance, and LIGHTING Load Quantify: the energy performance determine LIGHTING load for different SURFACE Colour reflectances to ascertain the measurable difference. Primary Research experiment and analysis: Derive Base Case for first part of the analysis where Wall (W), Floor (F) and Ceiling(C) are looked upon separately for variation. This model does not contain the Workplane (Wo) and Partitions (P). Simulation is carried out. Visual Comfort assessment- results obtained from simulations of these variations are compared to the standards to conform to their visual comfort requirements. These are then compared against their LIGHTING loads and group of W, F and C REFLECTANCE combinations with least connected loads are selected. Thereafter, Wo and P REFLECTANCE are considered as independent variables which are then looked upon separately as variations on the selected base cases from previous step.